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The hippopotamus (Hipopotamus amphibius), also known as the hippo was derived from the ancient Greek word for 'river horse'. This term describes them well as these massive herbivores spend more than sixteen hours a day submerged in rivers, lakes or mud to keep their body cool from the heat. The hippopotamus and the Pygmy Hippopotamus are the only two species in the family of Hippopotamidae. Weighing up to 3.5 tonnes, hippos are the third largest living land mammal by weight following after the elephant and the white rhinoceros. Despite their large bulky bodies, the hippopotamus can outrun humans both on land and in water. They are often considered to be one of the most dangerous animals for being responsible for the most human deaths in Africa. This report will explore the behavioural, structural and physiological adaptations of the hippopotamus as well as their habitat.
Habitat The hippopotamus is native to mainly the Western, Southern, Eastern and Central regions of Africa, also known as sub-Saharan Africa (see Figure #2). The hippo distribution once ranged from the Nile delta in Egypt, northern tip of Africa, all the way down to the southern Cape wetlands, occupying nearly every river system in the continent. However, due to increase hunting by humans for hippo meat and ivory tusks, their conservation status has become vulnerable and many are now confined in protected areas or areas undisturbed by humans. Another threat brought upon the species that has caused the 7.2% decline in hippo populations since 1994 is habitat loss.
Hippos today can be found inhabiting slow-moving freshwater lakes, rivers, streams, swamps or areas within national parks. Being amphibious animals, hippos need permanent water sources like rivers and lakes that are deep enough for them to submerge in. It should also be in a suitable range of grasslands for them to feed in. They often share the same habitat as one of their main predators, crocodiles. Crocodiles are considered as predators as they prey on young hippos. An average hippo pod is led by a dominant bull that presides over a stretch of river 250m long containing 5 to 30 females and young. Hippos live in pods of up to 30 individuals (see Figure #3). The largest groups of hippos inhabit areas in Central Africa following the Nile River Valley in East Africa.
To keep cool from the blazing African heat, hippos spend most of the day submerged in water or mud. This allows them to maintain their body temperature and to prevent their skin from drying out. Hippos also prefer to bask on the shore in areas undisturbed by humans. At dusk, hippos leave the water and travel inland individually (females and their young travel together) up to 30km to graze on short grass. Hippos choose to feed at night in order to protect their sensitive skin from the sun. Although there are sufficient amounts of water plants in the areas they spend their day in, hippos still prefer travelling long distances to feed. Every night, they can spend 4 or 5 hours consuming up to 60kg of grass.
Hippos, especially bulls are very aggressive and territorial when it comes to defending their water territory from trespassers. They are not territorial on land and if they feel threatened they will run for water. Likewise, female hippos are also aggressively towards intruders when it comes to protecting their young. Despite the fact hippos are herbivores, there have been numerous reports of hippos capsizing small boats that have intruded in their territory and bitting their occupants to their death. They account for more human deaths than any other African animal including crocodiles and lions.
Adaptations Structural Adaptation #1
One particular structural adaptation of the hippo is their eyes. Hippo’s eyes are very well adapted for aquatic life. Firstly, their eyes, along with their ears and nostrils, are positioned on top of the head allowing it to see (breathe and hear as well) while keeping most of the body submerged in water (see Figure #5). With this feature, hippos could stay underwater in their aquatic habitat and at the same time monitor their surrounding environment above the surface. Secondly, their eyes are covered by a clear membrane for protection. It also enables them to have a clear vision underwater. Climate change may have been the main environmental influenc to the change in the hippo’s structural adaptations. It could have been the change of the hippo's habitat from mainly terrestrial to being mainly aquatic that caused their change. With their new semi-aquatic lifestyle, the hippo’s eyes shifting to the top of the skull (similar profile to crocodile's) is far better adapted for their life on land and in water. It may be that semi-aquatic animals spent so much time submerged in water; it would be more beneficial if they were able to have a clear view of predators both above and below surface.
Structural Adaptation #2 Another structural adaptation of the hippo is their mouth. What is unique about their mouth is that it can open up to an angle of 150 degrees (see Figure #6). Their mouth measures up to 1.2m in length with a pair of canine teeth over 50cm long in each jaw. In fact, when hippo are seen ‘yawning’, they are actually signalling a threat to intruders by showing off its large teeth. The hippo’s mouth is perfectly structured for them to use as their deadly weapon. With their sharp canines and enormous mouth, hippos can defend themselves as well as attack mating or territorial rivals. It’s not uncommon to find hippos engaged in ‘mouth-to-mouth’ combat, ramming one another with mouths open or striking major gashes with their canines on one another. In fact, hippos are so strong with their mouths, they can easily rip off a human limb. Their canines are very much pulled to use during the mating season. During this time, hippo bulls will claim to be the dominate male of a length of shoreline and defend it, sometimes even killing a rival. Such events have added more environmental pressure for the hippo to increase the width and breadth of their mouth and teeth. Another environmental pressure is gradual habitat loss. Overtime, hippos have less shorelines to claim, therefore the competition between hippo bulls increase, thus larger mouths and teeth are more beneficial to win a fight. Behavioural Adaptation #1
What is interesting about the hippo’s behaviour is that they have well adapted to an existing social system displayed through a hierarchy. As mentioned before, on average, a hippo pod consists of up to 30 individuals patrolled by one dominant male, usually at least 20 years old. Within a pod, females tend to bask with females, bachelors with bachelors and the dominant bull on his own. This individual holds the position of alpha male in the group defending his stretch of river to up to 10 years until a younger rival challenges him in a ‘mouth-to-mouth’ combat and possibly end his dominance. The behaviour of having a social ranking system helps the species by giving the pod extra protection from the bull. This creates a more secure environment especially for the hippo young, thus allowing them a better chance of survival to carry on the generation. The environmental pressure that could have given rise to this adaptation may have been climate change. There might have been a time where the earth’s climate caused periods of drought causing limited pools of water. With water being the hippo’s much preferred habitat, droughts would have caused overcrowding resulting in a disruption in the hippo’s hierarchy system. It may be that only the most aggressive of the hippos were able to fight for these limited pools of water. Thus, they became the leaders of their pods and territory.
Behavioural Adaptation #2 A very unique behavioural adaptation of the hippo is that they scatter their faeces by whisking their tail to mark their territories. It is also used between hippo bulls at their territory’s borders. A hippo’s stubby and bristled tail measures to about 28-30cm. When hippos defecate, their tail spins rapidly like a propeller and distributes the excrement far and wide in all directions. This messy behaviour is mostly performed in the water as it spreads the faeces to a much further distance than on land. Hippos are retromingent animals, therefore their faeces are often mixed with urine. Not only do hippos use this behavioural adaptation for marking their territory, but it is also used as a mating ritual. The need for a dominance struggle and the ongoing change of habitat due to climate change puts more pressure on the species to have this behaviour. Hippos have a natural instinct of being terrestrial, thus hippo bulls are constantly fighting for the position of alpha male in the group. During the time of long-term climate changes, habitat environments changed as well causing the male hippos to have less to claim as their territory. This adaptation has helped hippo bulls especially by giving them an advantage to attract females despite their habitat loss. It is also more favourable for hippos to have a way to protect themselves by warning off other hippo bulls and preventing themselves from being killed or injured in a fight. Physiological Adaption #1 One particular physiological adaptation of the hippo is their secretion of sweat. This feature allows them to secrete a layer of thick, red-orange mucous from their pores to protect their skin from the sun. Japanese researchers found two unstable pigments within the secretion, the red pigment and orange pigment. Their results found that both pigments contained UV-absorbing molecules. This feature is very useful to hippos as they have very sensitive skin. Similar to their closest living relatives, cetaceans i.e dolphins and whales , hippos have practically no hair, therefore exposing their skin from the sun's powerful rays. Not only does this substance protect hippo’s skin when they are out of the water, it also keeps their skin moist and helps regulate their body temperature. The environmental pressure that would have given rise to this feature is their semi-aquatic lifestyle. Living in water has led to a pressure towards hairlessness, mainly because hair would cause drag for swimming and extra drying time for wet hair. Without hair, the skin could no longer be protected from the sun by fur. Therefore, specialized sweat became the solution to the problem. The Japanese research team also found that the red pigment had the effect of restraining the growth of some microbes thus preventing infection. This feature is also very important to hippo bulls as they are often involved in gruesome fights (usually for territorial challenges) in the wild with other hippos causing deep wounds and cuts (see Figure #4). Such events provided evolutionary pressure to make their skin produce their own antibiotics to prevent their exposed injuries to infection. Bibliography 1. African Wildlife Foundation. (2007). Hippopotamus. Retrieved on July 2nd, 2010 from http://www.awf.org/content/wildlife/detail/hippopotamus
2. Animal Fact Guide. (1999). Hippopotamus. Retrieved on July 22nd, 2010, from http://www.animalfactguide.com/animalfacts/hippopotamus/
3. Dee’s Hippo World. (n.d.) Hippopotamus Facts. Retrieved on July 22nd, 2010, from http://www.deeshippoworld.com/hippopotamus-facts.htm
4.Feldhake, G. (2005) Hippos: Natural History and Convention. Retrieved on July 23rd, 2010, from http://books.google.com.hk/books?id=KxYlHEh7Ff4C&pg=PA14&lpg=PA14&dq=hippo+environment+pressure+adaptation&source=bl&ots=fZoZhIOcwO&sig=rO_iI0dYy3re4sEhrVA0uHvIrJQ&hl=zh-TW&ei=r_hHTKm5J5LGcMLEhNcM&sa=X&oi=book_result&ct=result&resnum=4&ved=0CCsQ6AEwAw#v=onepage&q=hippo%20environment%20pressure%20adaptation&f=f 5. Kid Cyber (2006). Hippopotamus. Retrieved on July 22nd, 2010, from http://www.kidcyber.com.au/topics/hippo.htm
6. National Geographic. (n.d.) Hippopotamus. Retrieved on July 22nd, 2010, from http://animals.nationalgeographic.com/animals/mammals/hippopotamus.html
7. Out to Africa. (2007) Hippo. Retrieved on July 25nd, 2010, from http://www.outtoafrica.nl/animals/enghippo.html?zenden=2&subsoort_id=2&bestemming_id=1
8. San Diego Zoo. (n.d) Mammals: Hippopotamus. Retrieved on July 24nd, 2010, from http://www.sandiegozoo.org/animalbytes/t-hippopotamus.html
9. Science News For Kids. (2004). Hippo Sweat is Natural Sunscreen. Retrieved on July 3rd, 2010, from http://www.sciencenewsforkids.org/articles/20040602/Note2.asp
10. The Big Zoo. (n.d.) Hippopotamus. Retrieved on July 22nd, 2010, from http://www.thebigzoo.com/Animals/Hippopotamus.asp
11. Wikipedia. (2010). Hippopotamus. Retrieved on July 3rd, 2010 from http://en.wikipedia.org/wiki/Hippopotamus
12. Wild Watch. (2006). Hippos. Retrieved on July 23rd, 2010, from http://www.wildwatch.com/living_library/mammals-2/hippo
The hippopotamus (Hipopotamus amphibius), also known as the hippo was derived from the ancient Greek word for 'river horse'. This term describes them well as these massive herbivores spend more than sixteen hours a day submerged in rivers, lakes or mud to keep their body cool from the heat. The hippopotamus and the Pygmy Hippopotamus are the only two species in the family of Hippopotamidae. Weighing up to 3.5 tonnes, hippos are the third largest living land mammal by weight
Scientific Classification
Kingdom: Animalia
Phylum: Choradate
Class: Mammalia
Order: Artiodactyla
Family: Hippootamidae
Genus: Hippopotamus (genus)
Species: H. amphibius
Labelled diagram of the hippopotamus
Habitat
The hippopotamus is native to mainly the Western, Southern, Eastern and Central regions of Africa, also known as sub-Saharan Africa (see Figure #2). The hippo distribution once ranged from the Nile delta in Egypt, northern tip of Africa, all the way down to the southern Cape wetlands, occupying nearly every river system in the continent. However, due to increase hunting by humans for hippo meat and ivory tusks, their conservation status has become vulnerable and many are now confined in protected areas or areas undisturbed by humans. Another threat brought upon the species that has caused the 7.2% decline in hippo populations since 1994 is habitat loss.
Hippos today can be found inhabiting slow-moving freshwater lakes, rivers, streams, swamps or areas within national parks. Being amphibious animals, hippos need permanent water sources like rivers and lakes that are deep enough for them to submerge in. It should also be in a suitable range of grasslands for them to feed in. They often share the same habitat as one of their main predators, crocodiles. Crocodiles are considered as predators as they prey on young hippo
To keep cool from the blazing African heat, hippos spend most of the day submerged in water or mud. This allows them to maintain their body temperature and to prevent their skin from drying out. Hippos also prefer to bask on the shore in areas undisturbed by humans. At dusk, hippos leave the water and travel inland individually (females and their young travel together) up to 30km to graze on short grass. Hippos choose to feed at night in order to protect their sensitive skin from the sun. Although there are sufficient amounts of water plants in the areas they spend their day in, hippos still prefer travelling long distances to feed. Every night, they can spend 4 or 5 hours consuming up to 60kg of grass.
Hippos, especially bulls are very aggressive and territorial when it comes to defending their water territory from trespassers. They are not territorial on land and if they feel threatened they will run for water. Likewise, female hippos are also aggressively towards intruders when it comes to protecting their young. Despite the fact hippos are herbivores, there have been numerous reports of hippos capsizing small boats that have intruded in their territory and bitting their occupants to their death. They account for more human deaths than any other African animal including crocodiles and lions.
Adaptations
Structural Adaptation #1
Another structural adaptation of the hippo is their mouth. What is unique about their mouth is that it can open up to an angle of 150 degrees (see Figure #6). Their mouth measures up to 1.2m in length with a pair of canine teeth over 50cm long in each jaw. In fact, when hippo are seen ‘yawning’, they are actually signalling a threat to intruders by showing off its large teeth. The hippo’s mouth is perfectly structured for them to use as their deadly weapon. With their sharp canines and enormous mouth, hippos can defend themselves as well as attack mating or territorial rivals. It’s not uncommon to find hippos engaged in ‘mouth-to-mouth’ combat, ramming one another with mouths open or striking major gashes with their canines on one another. In fact, hippos are so strong with their mouths, they can easily rip off a human limb. Their canines are very much pulled to use during the mating season. During this time, hippo bulls will claim to be the dominate male of a length of shoreline and defend it, sometimes even killing a rival. Such events have added more environmental pressure for the hippo to increase the width and breadth of their mouth and teeth. Another environmental pressure is gradual habitat loss. Overtime, hippos have less shorelines to claim, therefore the competition between hippo bulls increase, thus larger mouths and teeth are more beneficial to win a fight.
Behavioural Adaptation #1
Behavioural Adaptation #2
A very unique behavioural adaptation of the hippo is that they scatter their faeces by whisking their tail to mark their territories. It is also used between hippo bulls at their territory’s borders. A hippo’s stubby and bristled tail measures to about 28-30cm. When hippos defecate, their tail spins rapidly like a propeller and distributes the excrement far and wide in all directions. This messy behaviour is mostly performed in the water as it spreads the faeces to a much further distance than on land. Hippos are
Physiological Adaption #1
One particular physiological adaptation of the hippo is their secretion of sweat. This feature allows them to secrete a layer of thick, red-orange mucous from their pores to protect their skin from the sun. Japanese researchers found two unstable pigments within the secretion, the red pigment and orange pigment. Their results found that both pigments contained UV-absorbing molecules. This feature is very useful to hippos as they have very sensitive skin. Similar to their closest living relatives, cetaceans i.e dolphins and whales , hippos have practically no hair, therefore exposing their skin from the sun's powerful rays. Not only does this substance protect hippo’s skin when they are out of the water, it also keeps t
Bibliography
1. African Wildlife Foundation. (2007). Hippopotamus. Retrieved on July 2nd, 2010 from http://www.awf.org/content/wildlife/detail/hippopotamus
2. Animal Fact Guide. (1999). Hippopotamus. Retrieved on July 22nd, 2010, from http://www.animalfactguide.com/animalfacts/hippopotamus/
3. Dee’s Hippo World. (n.d.) Hippopotamus Facts. Retrieved on July 22nd, 2010, from http://www.deeshippoworld.com/hippopotamus-facts.htm
4.Feldhake, G. (2005) Hippos: Natural History and Convention. Retrieved on July 23rd, 2010, from http://books.google.com.hk/books?id=KxYlHEh7Ff4C&pg=PA14&lpg=PA14&dq=hippo+environment+pressure+adaptation&source=bl&ots=fZoZhIOcwO&sig=rO_iI0dYy3re4sEhrVA0uHvIrJQ&hl=zh-TW&ei=r_hHTKm5J5LGcMLEhNcM&sa=X&oi=book_result&ct=result&resnum=4&ved=0CCsQ6AEwAw#v=onepage&q=hippo%20environment%20pressure%20adaptation&f=f
5. Kid Cyber (2006). Hippopotamus. Retrieved on July 22nd, 2010, from http://www.kidcyber.com.au/topics/hippo.htm
6. National Geographic. (n.d.) Hippopotamus. Retrieved on July 22nd, 2010, from http://animals.nationalgeographic.com/animals/mammals/hippopotamus.html
7. Out to Africa. (2007) Hippo. Retrieved on July 25nd, 2010, from http://www.outtoafrica.nl/animals/enghippo.html?zenden=2&subsoort_id=2&bestemming_id=1
8. San Diego Zoo. (n.d) Mammals: Hippopotamus. Retrieved on July 24nd, 2010, from http://www.sandiegozoo.org/animalbytes/t-hippopotamus.html
9. Science News For Kids. (2004). Hippo Sweat is Natural Sunscreen. Retrieved on July 3rd, 2010, from http://www.sciencenewsforkids.org/articles/20040602/Note2.asp
10. The Big Zoo. (n.d.) Hippopotamus. Retrieved on July 22nd, 2010, from http://www.thebigzoo.com/Animals/Hippopotamus.asp
11. Wikipedia. (2010). Hippopotamus. Retrieved on July 3rd, 2010 from http://en.wikipedia.org/wiki/Hippopotamus
12. Wild Watch. (2006). Hippos. Retrieved on July 23rd, 2010, from http://www.wildwatch.com/living_library/mammals-2/hippo